1. Field of the Invention
The present general inventive concept relates to a stereoscopic projection system with a plurality of projectors, and more particularly, to a stereoscopic projection system that is capable of minimizing a distance between viewing zones without narrowing a distance between image projectors and controlling the distance between the viewing zones of the image projectors.
2. Description of the Related Art
Stereoscopy has been widely researched as a way of displaying a stereoscopic image with a stereoscopic projection system. In the stereoscopy, two images representing two perspectives of the same object are respectively provided to left and right eyes of a viewer to create a three-dimensional image. Since the stereoscopy utilizes a pair of two-dimensional images, it provides an easy way of displaying the three-dimensional image with a high resolution and a high depth perception.
An autostereoscopic display is a type of the stereoscopy devices, which provides the three-dimensional image to the viewer without requiring the viewer to wear additional tools such as special glasses. In the autostereoscopic display, the viewer should be positioned at a viewer position, where a left-eye image and a right-eye image can be respectively provided to the left and right eyes of the viewer, for a three-dimensional viewing.
When the autostereoscopic display provides a plurality of views with a plurality of projectors, different stereoscopic images can be seen from different viewer positions within a viewing area. For example, the viewer can see the different stereoscopic images sequentially by changing his/her position within the viewing area.
The autostereoscopic display is disclosed in the following references:
1) Takanori Okoshi, “Three-Dimensional Imaging Techniques,” Academic Press New York, San Francisco, London, 1976 (hereinafter ‘Okoshi’);
2) U.S. Pat. No. 4,799,739, issued to C. Newswanger and entitled “Real time autostereoscopic display using holographic diffusers”; and
3) J-Y. Son, V. Bobrinev, “Autostereoscopic imaging systems based on holographic screen,” SPIE Proceedings, Vol. CR76, pp. 30-60, 2001.
FIG. 1 is a plan view schematically showing a conventional autostereoscopic projection system that can project a plurality of images (multi-view), as disclosed in Okoshi.
Referring to FIG. 1, a plurality of projectors P1, P2 . . . PM are horizontally arranged from a right side to a left side as seen by a viewer 35 to form a projector array 10, and a screen 20 is interposed between the viewer 35 and the projector array 10. The projector array 10 receives image signals of an object 0 from a camera array 1 to project a plurality of images on the screen 20. The camera array 1 includes a plurality of cameras P′1, P′2 . . . P′M that correspond to the projectors P1, P2 . . . PM, respectively. That is, the camera array 1 takes pictures of the object 0 from different angles and converts the pictures into the respective image signals, to provide the plurality of images to form a stereoscopic image of the object 0.
The screen 20 is a directional screen with a horizontal directivity. The screen 20 includes a condenser lens 21 and a one-dimensional diffuser 25. The condenser lens 21 condenses the plurality of images that are simultaneously projected by the projectors P1, P2 . . . PM of the projector array 10. The one-dimensional diffuser 25 diffuses the incident images in a vertical direction while maintaining the horizontal directivity of the screen 20 to increase a degree of freedom in the vertical direction of the screen 20. Therefore, the viewer 35 can view the plurality of images projected on the screen 20 by locating his/her eye pupils at an exit pupil position 31 (viewer position) spaced a distance LV apart from the screen 20. FIG. 2 shows a plurality of screen images I1, I2 . . . IM viewed from the viewer position (exit pupil position 31) of the conventional autostereoscopic projection system of FIG. 1. Referring to FIGS. 1 and 2, the plurality of images I1, I2 . . . IM, which are respectively projected from the projectors P1, P2 . . . PM of the projector array 10, are arranged in a horizontal direction (X) with a distance SV therebetween, showing a vertical diffusion due to the diffuser 25 and the horizontal directivity. The viewer 35 can view the different images of the same object 0 while changing his/her location.
The distance SV is equal to a distance SP (shown in FIG. 1) between the projectors multiplied by a magnifying power K (SV=K·SP). The distance SV should be set below an average distance between eyes of persons (65 mm), to provide stable three-dimensional images to the viewer. The magnifying power K denotes a magnification ratio of the autostereoscopic projection system, and it is given by an equation: K=LV/LP, where LV is a viewing distance between the screen 20 and the exit pupil position 31 and LP is a projecting distance between the projector array 10 and the screen 20. It may be assumed that the distance SV between the images is equal to the distance between viewing zones.
In the case of a multi-view display using a plurality of projectors, the distance SV is required to be below 3 mm to allow smooth change of the sequential images when the viewer changes his/her location.
In the conventional autostereoscopic projection system as shown in FIGS. 1 and 2, however, it is hard to reduce the distance SV to be bellow 3 mm to allow smooth change of the sequential images when the viewer changes his/her location, because the distance SV is proportional to the distance SP between projectors (SV=K·SP) and SP is about 100 mm. The distance SV can be adjusted to satisfy the above requirement by increasing inversed magnifying power 1/K above 30. In this case, however, the distance LP becomes much larger than the distance LV (30 times or more), thereby increasing a size of the conventional autostereoscopic projection system excessively. Therefore, the requirement to decrease the distance SV to allow smooth change of the sequential images when the viewer changes his/her location cannot be achieved with the conventional autostereoscopic projection system.